#pragma comment(linker, "/STACK:10000000")
#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <iomanip>
#include <set>
#include <map>
#include <cstdio>
#include <cassert>
#include <string>
#include <cstring>
#define ldb long double
#define ll long long
#define fi first
#define se second
#define fill(a, c) memset(a, c, sizeof(a))
#define sqr(a) ((a) * (a))
#define nextLine() {int c = 0; while((c = getchar()) != 10 && c != EOF);}
#define getBit(mask, k) (((mask) / pw[k]) % pw[1])
#define setBit(mask, k, l) (((mask) / pw[k + 1] * pw[1] + (l)) * pw[k] + ((mask) % pw[k]))
#define debug(a) cerr << #a << " = " << a << " ";
#define debugl(a) cerr << #a << " = " << a << "\n";
#define mp(a, b) make_pair(a, b)
#define pb(a) push_back(a)
#define ff first
#define ss second 
const ldb LDINF = 9128739847123.00;
const ldb eps = 1e-9;
const int inf = 1 << 28;
const ldb pi = fabsl(atan2l(0.0, -1.0));
using namespace std;

vector <ll> all;
ll n, k;

void load()
{
	cin >> n >> k;
	{
	for (int i = 1; i <= 10; i++)
	{
		for (int j = 0; j < (1 << i); j++)
		{
			ll num = 0;
			for (int k = 0; k < i; k++)
			{
				if (j & (1 << k))
					num = num * 10 + 4;
				else num = num * 10 + 7;
			}
			all.pb(num);
		}
	}
	sort(all.begin(), all.end());
	}
}

ll fact[14];

int count(int l, int r)
{
	int pos1 = 0;
	int pos2 = 0;
	for (; pos1 < all.size() && all[pos1] < l; pos1++);
	for (; pos2 < all.size() && all[pos2] <= r; pos2++);
	return pos2 - pos1;
}

bool lucky(int a)
{
	bool ok = true;
	while (a && ok)
	{
		if (a % 10 != 4 && a % 10 != 7) 
			ok = false;
		a /= 10;	
	}
	return ok;
}

ll a[1123];

void solve()
{
	
	fact[0] = 1;
	for (int i = 1; i <= 13; i++)
		fact[i] = fact[i - 1] * i;
   	if (n <= 13 && k > fact[n])
	{
		printf("-1");
		return;
	}
	ll res = 0;
	int i = 1;
	int add = 0;
	int begin = 1;
	if (n - 1 > 13)
	{
		res += count(1, n - 14);
	//	cerr << count(1, n - 14) << "\n";
		add = n - 14;
		i = n - 13;
		begin = n - 13;
	}
	k--;
//	cerr << begin << " " << add << " " << i << "\n";
	int sz = 0;
	for (sz = 0; i <= n; sz++, i++)
	{
		a[sz] = k / fact[n - i];
		k %= fact[n - i];
	}
	for (int l = sz - 1; l >= 0; l--)
	{
		for (int j = l + 1; j < sz; j++)
		{
			if (a[j] >= a[l])
				a[j]++;
		}
	}

	for (int i = 0; i < sz; i++)
		if (lucky(add + a[i] + 1) && lucky(begin + i)) res++;
	cout << res;
}

#define file "c"
int main()
{
	#ifndef ONLINE_JUDGE
		freopen(file".in", "rt", stdin);
		freopen(file".out", "wt", stdout);
	#endif
	load();
	solve();
	return 0;
}
